Special Issue Information

Dear Colleagues,

Studies of cancer in occupational settings have contributed greatly to our understanding of cancer risk. About one third of the factors identified as definite or probable human carcinogens were first investigated in the workplace. However, there are many current occupational exposures that are putative carcinogens, and many new and emerging exposures that make further research in this area necessary. Additionally, much of our understanding about occupational cancer has been obtained from studies largely composed of white men in developed countries. The movement of industry from developed to developing countries underscores the need for future investigations to include more diverse populations.

For this special issue on Occupational Cancer, we would be happy to consider papers that report on a variety of topics. Reports of particular interest include results from epidemiologic investigations, including those that incorporate molecular techniques. We are also interested in reports on occupational exposure assessment methods and would consider papers that summarize the knowledge on a particular topic such as specific occupational exposures or jobs/workplaces.

Abstract: We conducted a meta-analysis focusing on studies with high potential for trichloroethylene (TCE) exposure to provide quantitative evaluations of the evidence for associations between TCE exposure and kidney, liver, and non-Hodgkin lymphoma (NHL) cancers. A systematic review documenting essential design features, exposure assessment approaches, statistical analyses, and potential sources of confounding and bias identified twenty-four cohort and case-control studies on TCE and the three cancers of interest with high potential for exposure, including five recently published case-control studies of kidney cancer or NHL. Fixed- and random-effects models were fitted to the data on overall exposure and on the highest exposure group. Sensitivity analyses examined the influence of individual studies and of alternative risk estimate selections. For overall TCE exposure and kidney cancer, the summary relative risk (RRm) estimate from the random effects model was 1.27 (95% CI: 1.13, 1.43), with a higher RRm for the highest exposure groups (1.58, 95% CI: 1.28, 1.96). The RRm estimates were not overly sensitive to alternative risk estimate selections or to removal of an individual study. There was no apparent heterogeneity or publication bias. For NHL, RRm estimates for overall exposure and for the highest exposure group, respectively, were 1.23 (95% CI: 1.07, 1.42) and 1.43 (95% CI: 1.13, 1.82) and, for liver cancer, 1.29 (95% CI: 1.07, 1.56) and 1.28 (95% CI: 0.93, 1.77). Our findings provide strong support for a causal association between TCE exposure and kidney cancer. The support is strong but less robust for NHL, where issues of study heterogeneity, potential publication bias, and weaker exposure-response results contribute uncertainty, and more limited for liver cancer, where only cohort studies with small numbers of cases were available.

Abstract: Objective:Cancer has been recognized to have environmental origin, but occupational cancer risk studies have not been fully documented. The objective of this paper was to identify occupations and industries with elevated colon cancer risk based on lifetime occupational histories collected from 15,463 incident cancer cases. Method:A group matched case-control design was used. All cases were diagnosed with histologically proven colon cancers, with cancer controls being all other cancer sites, excluding rectum, lung and unknown primary, diagnosed at the same period of time from the British Columbia Cancer Registry. Data analyses were done on all 597 Canadian standard occupation titles and 1,104 standard industry titles using conditional logistic regression for matched data sets and the likelihood ratio test. Results: Excess colon cancer risks was observed in a number of occupations and industries, particularly those with low physical activity and those involving exposure to asbestos, wood dusts, engine exhaust and diesel engine emissions, and ammonia. Discussion: The results of our study are in line with those from the literature and further suggest that exposure to wood dusts and to ammonia may carry an increased occupational risk of colon cancer.

Abstract: Despite showing no evidence of carcinogenicity in laboratory animals, the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been associated with non-Hodgkin lymphoma (NHL) in some human epidemiology studies, albeit inconsistently. We matched an existing cohort of 2,4-D manufacturing employees with cancer registries in three US states resulting in 244 cancers compared to 276 expected cases. The Standardized Incidence Ratio (SIR) for the 14 NHL cases was 1.36 (95% Confidence Interval (CI) 0.74–2.29). Risk estimates were higher in the upper cumulative exposure and duration subgroups, yet not statistically significant. There were no clear patterns of NHL risk with period of hire and histology subtypes. Statistically significant results were observed for prostate cancer (SIR = 0.74, 95% CI 0.57–0.94), and “other respiratory” cancers (SIR = 3.79, 95% CI 1.22–8.84; 4 of 5 cases were mesotheliomas). Overall, we observed fewer cancer cases than expected, and a non statistically significant increase in the number of NHL cases.

Abstract: Dichloromethane (methylene chloride) is a widely used chlorinated solvent. We review the available epidemiology studies (five cohort studies, 13 case-control studies, including seven of hematopoietic cancers), focusing on specific cancer sites. There was little indication of an increased risk of lung cancer in the cohort studies (standardized mortality ratios ranging from 0.46 to 1.21). These cohorts are relatively small, and variable effects (e.g., point estimates ranging from 0.5 to 2.0) were seen for the rarer forms of cancers such as brain cancer and specific hematopoietic cancers. Three large population-based case-control studies of incident non-Hodgkin lymphoma in Europe and the United States observed odds ratios between 1.5 and 2.2 with dichloromethane exposure (ever exposed or highest category of exposure), with higher risk seen in specific subsets of disease. More limited indications of associations with brain cancer, breast cancer, and liver and biliary cancer were also seen in this collection of studies. Existing cohort studies, given their size and uneven exposure information, are unlikely to resolve questions of cancer risks and dichloromethane exposure. More promising approaches are population-based case-control studies of incident disease, and the combination of data from such studies, with robust exposure assessments that include detailed occupational information and exposure assignment based on industry-wide surveys or direct exposure measurements.

Abstract: Objectives: To assess whether cancer incidence, mainly from lymphohaematopoietic tumours and breast cancer, and mortality were increased in a cohort of Swedish sterilant workers exposed to low levels of ethylene oxide (EtO), updated with 16 more years of follow up. Methods: The mortality and cancer incidence 1972–2006 experienced by a cohort of 2,171 male and female workers employed for at least one year in two plants producing medical equipment sterilised with EtO were investigated. Individual cumulative exposure to EtO was assessed by occupational hygienists. Cause-specific standardized rate ratios were calculated using the regional general population as a comparison for mortality (SMR) and cancer incidence (SIR). Internal Poisson-regression analyses were performed for selected causes. Results: The median cumulative exposure to EtO was 0.13 ppm-years. The overall cancer incidence was close to unity (SIR 0.94, 95% CI 0.82–1.08). Eighteen cases of lymphohaematopoietic cancer were observed (SIR 1.25, 95% CI 0.74–1.98). A healthy worker effect was indicated from a significantly decreased overall mortality and mortality from cardiovascular diseases. Internal analyses found significantly increased rate ratios for breast cancer for the two upper quartiles of cumulative exposure as compared to the lowest 50% of the cohort (IRR 2.76, 95% CI 1.20–6.33 and IRR 3.55, 95% CI 1.58–7.93). Conclusions: The findings from this updated study indicate limited or low risks for human cancer due to occupational exposure from ethylene oxide at the low cumulative exposure levels in this cohort. However a positive exposure-response relation with breast cancer was observed though.